WO2006137077A1

WO2006137077A1 - A pointing device with absolute and relative positioning capability

Info

Publication number: WO2006137077A1
Application number: PCT/IN2005/000209
Authority: WO
Inventors: Shekhar Ramachandra Borgaonkar; Prasenjit Dey
Original assignee: Hewlett-Packard Development Company, L.P.
Priority date: 2005-06-20
Filing date: 2005-06-20
Publication date: 2006-12-28

Abstract

The invention relates to a pointing device capable of determining its coarse absolute location in addition to its relative displacement on a surface. A possible embodiment of the pointing device comprises an illuminating source, a sensor means and a processor. The illuminating source illuminates a portion of the surface. The sensor means detects optical information coming from at least a spot of the illuminated portion of the surface. The surface on which the pointing device is moved is divided into a plurality of non-overlapping fields, wherein the fields together continuously cover the surface. Each of the fields is associated with a unique color information. A digital image of the surface is also stored, preferably in a memory, and made accessible for the processor.

Description

A pointing device with absolute and relative positioning capability

Field of the Invention

The present invention relates generally to pointing devices. In particular, the invention relates to a pointing device with absolute and relative pointing capability.

Background of the Invention

The usage of various pointing devices, e.g. touch pads, light pens or mice, etc., is an integral part of our everyday life. Some of these devices, connected generally to computers, are basically used for pointing to and selecting different objects displayed on a screen and for launching the application (s) associated with the object selected. Other pointing devices are also capable of inputting and/or digitizing ' data into the memory of a computer. In most cases, for the proper operation it is sufficient to sense only the relative changes in position, i.e. the relative displacement of the pointing device on the surface on which it has been put down and is^' moved, whereas the absolute location information of the device is not utilized.

The significance of precise knowledge of the absolute location information of a pointing device on a surface has been recognised for a long time. It has also been realized that the exploitation of this additional information can provide a natural way of interaction with a computer or with an apparatus that is computerized. Therefore, various types of pointing devices providing both the absolute and relative position data during their operation have been constructed. The operation of the first type of such pointing devices is based on a pattern recognition algorithm. Here, the device is _ O _

arranged on a surface provided with a special pattern. When the device is moved over the surface, it captures an image of a portion of the surface and the absolute position is identified on the basis of the pattern appearing in the captured image. The position identification is unambiguous since any spot on the surface is uniquely encoded by the associated pattern detail. However, this type of position determination requires considerable computing resources for processing the pattern, that is, to decode the absolute position information.

In another type of the pointing devices the position on a surface is determined by means of electromagnetic or acoustic transmitter and receiver (s). The transmitter is incorporated into the pointing device, while the receiver (s) is/are arranged separately, generally as part of a specially manufactured pad or tablet on which the pointing device is moved. The precise positioning of the pointing device takes place via electromagnetic sensing (used in tablet personal computers) or via acoustic triangulation. A drawback of this solution is that the use of additional elements, such as a transmitter or a receiver, and of a separate pad or tablet increases production costs, decreases reliability and leads to a relatively complicated technique.

A further type of the pointing device simply uses colors for determining the absolute position of the device on a surface. The concept here utilizes the change in the color of the surface and the sensing of the actual color at the momentary locations of the pointing device. Here, the absolute position information of the device at any given instant can be uniquely determined if the discretely preset locations and the associated colors are in one-to-one correspondence, that is, when a bijective mapping exists between the locations and the colors. In general, a pointing device with both absolute and relative positioning capability is movable over a rectangular pad and includes an illuminating source, preferably a light-emitting diode (LED) , for illuminating a portion of the pad under the device and a sensing mechanism, preferably a CCD sensor, for detecting the reflected light coming from the illuminated portion. The pad is formed with a surface continuously covered by a plurality of non-overlapping fields, each of which represents a uniquely coded position on the pad. Each uniquely coded position is basically made up of a percentage of a first color and a percentage of a second color differing from the first one. The percentage of the first color is changing in a well-defined manner along a first axis, e.g. from the left margin of the pad to the right margin thereof, and the percentage of the second color is also changing in a definite way, but along a second axis perpendicular to the first one, e.g. from the bottom margin of the pad to the top margin thereof. Thus, both percentages of color has a respective gradient along the corresponding axis, and the surface of the pad is provided with an overall gradient comprised of the two separate gradients superimposed onto each other. By measuring the intensities of the two colors at any given location with the sensing mechanism by detecting the reflected light, the absolute position of the device can be determined; from the measured intensity values, the accurate position coordinates along each of the two perpendicular axes can be obtained by applying a reverse calculation utilizing the corresponding gradient .

A major disadvantage of this particular solution is that due to ageing of the LED, the spectral composition of the emitted light changes. This leads to a change in the reflected light detected by the sensing mechanism too, and as a consequence, the calculation starting with the gradient applied on the pad surface can lead to incorrect position data. This deficiency emerging with time becomes more relevant when a more accurate absolute position determination is required. The finer the gradient densities are the larger will be the chances for obtaining incorrect position results. Therefore, this system requires a continuous supervision, i.e. a calibration performed from time to time by the end-user of the device.

A common feature of all types of the above pointing devices lies in the objective of accomplishing the highest possible positioning resolution. Nevertheless, there are certain applications (eg. when complex forms or queries are to be completed) wherein there is no need for accurately knowing the absolute position of the pointing device, and a rough knowledge of the absolute position thereof is satisfactory.

The determination of coarse position information does not require the above outlined expensive and less reliable techniques. Hence, it is an object of the present invention to provide a pointing device wherein the coarse absolute position and the relative changes in position can both be determined in a simple and inexpensive manner.

Summary of the Invention

The above object has been solved by providing a pointing device, in particular an optical mouse system or a digital pen system, capable of the simultaneous determination of its coarse absolute location and the relative changes in its position when being moved over a surface. Both of the optical mouse and the digital pen according to the invention include an illuminating source, a sensor means and a processor. The illuminating source illuminates a portion of the surface. The sensor means detects optical information coming from at least a spot of the illuminated portion of the surface. The surface on which the mouse/digital pen can move is divided into a plurality of non-overlapping fields, wherein the fields together continuously cover the surface and each of them is ™ o ^™ associated with a unique color information. A digital image of the surface is stored in a memory and made accessible for the processor. Starting from the detected optical information, the processor determines on the one hand the coarse absolute location of the mouse/digital pen by comparing the color information component of the optical information with the stored digital image of the surface, and on the other hand calculates the relative changes in position by comparing two pieces of optical information obtained in consecutive sensings.

Brief Description of the Drawings

An embodiment of the invention will be discussed in detail with reference to the following drawings.

Figure 1 shows a medium having a color coded surface area to be used as a pad on which a pointing device according to an embodiment of the invention can be placed and moved in any direction; Figure 2 shows an individual element of the color coded surface area in an enlarged view according to an embodiment of the invention;

Figure 3 (a) shows a pointing device according to an embodiment of the invention manufactured in the form of a mouse and arranged on the color coded surface area of the medium illustrated in Figure 1;

Figure 3 (b) shows a block diagram of the mouse type pointing device illustrated in Figure 3 (a) according to an embodiment of the invention; Figure 4 shows a flowchart for determining the coarse absolute position and the relative changes in position of a pointing device according to an embodiment of the invention; Figure 5 shows schematically a pointing device according to an alternate embodiment of the invention manufactured in the form of a pen; and Figure 6 shows an exemplary form which can be used in combination with the pointing device according to an embodiment of the invention for simple data inputting.

Detailed Description of the Invention

Referring to Fig. 1, a pad 100 according to an embodiment is shown. The pad 100 is provided with a positioning region 110 on one of its surfaces. In this particular embodiment, the positioning region 110 has a rectangular shape, however it can be of any shape. The positioning region 110 is divided into a plurality of non-overlapping fields 112 which together continuously cover the whole area of the positioning region 110. The fields 112 of the positioning region 110 can be of any size and shape. In the embodiment shown in Fig. 1 the fields 112 are chosen to be also rectangular. The number of the individual fields 112 can be chosen arbitrarily, and the fields 112 can be uniquely numbered.

As shown in Fig. 1, if for example a rectangular positioning region 110 with n rows and m columns is provided (wherein n, m ≥ 1, positive integers) , the total number of the fields 112 within the positioning region 110 will be n times m. In this case the numbering of a certain field can be simply achieved by assigning thereto the number of the row and the number of the column in which the given field is located, i.e. the field 112 being in the i-th row and in the j-th column (wherein 1 ≤ i ≤ n and 1 ≤ j ≤ m) of the positioning region 110 will be numbered as the ij-th element of the positioning region 110. It is noted here that the numbering of the fields 112 can be chosen arbitrary.

Furthermore, each field 112 has a uniform surface area and is provided with a unique color information. The detection of the color information allows an unambiguous identification of the fields 112. The absolute location data are encoded by the color information and they represent coarse absolute positions of the pointing device over the- positioning region 110. Here, the word "coarse" means that the absolute position information unambiguously specifies the field over which the pointing device is actually located, but provides no further information with regard to the exact position thereof within this field.

A position-encoding color information may include (i) the color of a certain field 112 or (ii) a combination of (at least) two distinct colors applied uniformly within the same field 112. In the first case, every field 112 of the positioning region 110 has a single individual color that differs from the colors of all other remaining fields. In the second case, the combination means a special pattern of two alternating colors. It should be appreciated that the colors can be chosen arbitrarily, however, colors with significantly differing hues are preferred. Using two distinct colors in each field 112 increases the set of positions that can be uniquely represented in the positioning region 110. In this way the resolution of the coarse absolute location of the pointing device can be increased.

Referring to Fig. 2, it shows the ij'-th field 112 of the positioning region 110 illustrated in Fig. 1, wherein the position-encoding color information is generated by the -use of two different colors in e.g. a chessboard-like pattern. Here, the field 112 is uniformly covered by tiny contiguous blocks 113, 114 of the two colors (represented by dotted and white regions, respectively) . The blocks 113, 114 can have any arbitrary shape, however, their sizes should be chosen to be much smaller than the size of the smallest field 112 of the positioning region 110.

The pad 100 with the fields 112 carrying the coarse absolute position information can be made of any material used in practice for manufacturing pads to be used in conjunction with pointing devices, in particular with optical mice. In an embodiment, the pad 100 is provided as a sheet of paper with the positioning region 110 printed thereon. The pad 100 can be supplied by the manufacturer of the pointing device together with the device or it can be prepared by the end-user as a part of the installation procedure of the device. In this latter case, the digitally stored image of the positioning region. 110, which is provided by the manufacturer on a suitable medium, can be simply printed by a standard color printer. Furthermore, the end-user of the device can customize the color information of the fields 112 in accordance with his/her needs or at his/her discretion. Nevertheless, if this takes place, the new settings of the positioning region 110 (i.e. the mapping between the fields 112 and the pieces of color information) must be saved and stored so. that the pointing device can operate appropriately.

Referring now to Figs. 3 (a) and 3 (b) , a possible embodiment of the pointing device in the form of a mouse 200 arranged on the pad 100 of Fig. 1 is illustrated. The mouse 200 can be a conventional optical mouse which is capable of providing the relative changes in its position when it moves. However, the known hardware components included in the mouse 200 are also used for detecting and processing another piece of information too, namely the color information uniquely associated with each of the individual fields 112. By detecting and processing this further information, the mouse 200 also becomes capable of providing its absolute position information over the pad 100.

The mouse 200 includes a housing 210, an illuminating source 220, a sensor means 230, a processor 240 and suitable connection means 228, and it can be moved freely on the pad 100 over the uniquely colored fields 112 thereof. The illuminating source 220 and the sensor means 230 are disposed on the underside of the housing 210 relatively close to each other. In a possible embodiment, the processor 240 is arranged within the housing 210 and is optionally associated with a suitable data storage means, preferably with a memory 245, containing the actual digital image of the positioning region 110. .

As the mouse 200 is moved on the pad 100, the illuminating source 220 emits a light beam 222 incident on a field 112 of the positioning region 110 and causing the illumination of a spot 115 thereon. The illuminating source 220 includes for example a light emitting diode (LED) emitting for example white light, although the invention is not limited to any particular illuminating light. Usage of the built-in illuminating source 220 and its adjacent arrangement to the sensor means 230 ensures that strayed light entering from the surroundings into the sensor means 230 cannot disturb the sensing process, and thus, enhances the reliability of the mouse 200.

As a consequence of the illumination by the light beam 222, a reflected light beam 224 arises from the spot 115 on the surface of the pad 100 which then reaches the sensor means 230. The sensor means 230 includes an optical sensor for detecting the reflected light beam 224. In an embodiment, a common and relatively inexpensive CMOS sensor is used as the sensor, the sensing mechanism of which is known for a person skilled in the relevant art. The reflected light beam 224 detected by the sensor means 230 carries optical information about the spot 115. The optical information includes color information associated with the sensed spot 115 and information characteristic to the surface quality/roughness of the positioning region 110 within the spot 115.

The sensor means 230 outputs the obtained optical information as a sensed information 226 which is then transferred to the processor 240 for being processed. The size of the sensed spot

115 detected by the sensor means 230 at a given instant is

° much smaller than the area of any of the separate fields 112, however, to uniquely identify the field 112, i.e. to unambiguously determine the coarse absolute position of the mouse 200, the spot 115 is large enough to provide the color information concerning the field 112 over which the mouse 200 is located. In particular, referring now to Fig. 2, this means that the size of the sensed spot is adjusted in such a way that it fully covers at least two blocks 113, 114 of different colors in case of the shown two-color color combination field 112. In general, if more than two colors are used within a field for providing the color information unambiguously, the size of the sensed spot is chosen to fully cover at least as many blocks as many different colors are present in a particular field 112.

In addition to delivering the color information, the sensor means 230 also provides the conventional information concerning the displacement of the mouse 200 (in the form of "photos" or shots taken successively of the sensed spots 115 as the mouse 200 is moved) . This defines the relative change in position of the mouse 200 within the positioning region 110 or just in one field 112.

The processor 240 is adapted to process the digital signals detected by the sensor means 230. On the one hand, by exploiting an algorithm known by the person skilled in the art, it compares the shots of the sensed spots 115 with the digital image of the positioning region 110 provided as being accessible by the processor 240, i.e. the image is stored either in the processor 240 itself or in the optional memory 245 associated with the processor 240 or in a storage medium of another device, such as a computer, to which the mouse 200 is connected. Processor 240 can be implemented by means of e.g. a Digital Signal Processor (DSP) chip, although the invention is not limited thereto.

The connection means 228 is used for transferring data from the mouse 200 to another device 250, such as a computer. The device 250 upon receiving the position and/or displacement data may further process them. In one embodiment, the connection means 228 is a wireless connection, such as radio frequency or infrared connection. An example of a radio frequency connection means is Bluetooth. The connection means

228 can also be provided as a wired connection, such as a serial or a parallel port or a Universal Serial Bus (USB) .

Referring now to Fig. 4, the operation of the optical mouse 200 is discussed in more detail. In case the pad 100 with the positioning region 110 comprised of the uniquely colored fields 112 is not provided by the manufacturer in a physical format, after installing the mouse 200 the pad 100 is prepared by printing the digital image of the positioning region 110 onto an ordinary sheet of paper in step 301. If the digital image of the positioning region 110, i.e. the color assignment of the fields 112 should be customized by the end-user, the digital image of the modified positioning region 110 is also stored in this step. When the pad 100 with the positioning region 110 is successfully provided, the mouse 200 is put down on the positioning region 110, and hence the system of the pad

100 and the mouse 200 is ready for use.

In step 302, as the "mouse 200 is moved on the pad 100, the illuminating source 220 illuminates the spot 115. The spot 115 reflects the light beam 224 which then reaches the sensor means 230 and is detected thereby in step 303. The reflected light beam 224 carries optical information about the spot 115 of the illuminated portion of the positioning region 110. The optical information comprises color information associated with the sensed spot 115 and further information characteristic to the surface quality/roughness of the positioning region 110 within the spot 115. The sensor means 230 outputs the obtained optical information as a signal of a sensed information 226 which is then, in step 304, transferred to the processor 240 for being processed.

In step 305, processing of the sensed information 226 takes place. Here, the processor 240 directly compares the color information component of the sensed information 226 with the stored digital image of the positioning region 110. Furthermore, the processor 240 also compares pieces of information characteristic to the quality of the positioning region 110 obtained in two consecutive detection events. This latter comparison takes place in the same manner as in the case of optical mice capable of providing only relative changes in position. It is noted here that in an embodiment, the coarse position location operation and the relative movement determination work independently. That is, the processor 240 carries out the two comparisons in two separate processing channels.

As a result of the above comparisons, in step 306, the coarse absolute position of the mouse 200 corresponding to the detected color information and the relative positional movement of the mouse 200 are determined separately, but simultaneously. Furthermore, the obtained position information data are transferred via the connection means 228 to the outside device 250, such as a computer, for further use or processing.

Referring now to Fig. 5, a possible further embodiment of the pointing device in the form of a digital pen 400 arranged on the pad 100 shown in Fig. 1 is illustrated. The digital pen 400 includes an elongated, generally tubular-shaped housing 410 closed at its one end and open at its other end, an illuminating source 420, a sensor means 430, a tip 440 and an electronics 450. The illuminating source 420 and the sensor means 430 are disposed at the open end of the housing 410 in the immediate vicinity of the tip 440, also relatively close to each other. The illuminating source 420 and the sensor means 430 are identical to the respective components of the mouse 200 shown in Fig. 3 (a) , and hence are not discussed in more detail. The tip 440 can be simply formed as a protruding element of the housing 410. In another embodiment, the tip 440 can be formed to be susceptible of writing with the pen 400. In this latter case, the tip 440 is suitably connected with an ink forming element (not shown) arranged preferably within the housing 410 which supplies the tip 440 with ink when the user moves the pen 400 over a suitable medium.

In Fig. 5, the term electronics 450 refers in general to the entirety of the electronic components utilized for the proper functioning of the pen 400. In particular, the electronics 450 includes e.g. a processor for carrying out the position determinations, and a suitable connection means for transferring data from the pen 400 to an external device, such as a computer, etc. The pen 400 also includes an optional data storage means, preferably a memory 445 connected to the electronics 450, for storing the digital image of the positioning region 110. In Fig. 5 an illuminating light beam 422 emitted by the illuminating source 420 and a reflected light beam 424 detected by the sensor means 430 are also illustrated. The operation of the pen 400 is similar to that of the mouse 200 shown in Figs. 3 (a) and 3 (b) , and hence is not discussed in more detail.

Fig. 6 shows an example of a form 600 which can be used in an embodiment. The form 600 illustrated in Fig. 6 is provided with four different fields 612-615, each having a different color or a combination of at least two colors. The fields 612- 615 are identified on the basis of the color information they carry. In an embodiment, the fields 612-615 are used for a simple and fast data inputting in a unique way when a pointing device according to an embodiment is used in combination with the form 600.

As the pointing device aims at determining only a coarse absolute position information from the color information detected by a suitable sensor means, and as the processing of the color information takes place in a less complex manner compared to pattern recognition widely used for this purpose, a relatively inexpensive low-end processor can be incorporated in the pointing device. In addition, the sensor means used for sensing of the color information can be implemented by a relatively inexpensive CMOS sensor. Furthermore, no extra hardware such as a separate pad or tablet or additional electronic components are needed. Therefore, a relatively inexpensive and simple pointing device with coarse absolute and fine relative positioning capability has been provided.

Although the present invention has been described based on a particular embodiment only, a person ordinary skilled in the art will readily recognize that further variations to the shown embodiment are also possible. These variations, nevertheless, also fall within the spirit and scope of the present invention.

Claims

What is claimed is:

1. A pointing device for determining coarse absolute location information on a surface divided into a plurality of non-overlapping fields, the pointing device comprising: an illuminating source for illuminating a portion of the surface, said portion corresponding to the actual location of said device over said surface; a sensor means for sensing a reflected light from said illuminated portion and designed to deliver different sensed signals in response to each of a plurality of unique optical properties associated with said fields of said surface; and a processor associated with a memory storing a comparison table between each of said unique properties and the field associated with said unique property, and using said sensed signal to identify the associated field on the basis of the comparison table and to deliver thereby a coarse location information.

2. The pointing device of claim 1, wherein the optical property comprises color .information.

3. The pointing device of claim 2, wherein the color information comprises the color of the respective field.

4. The pointing device of claim 2, wherein the color information comprises a pattern of at least two distinct colors used in the respective field.

5. The pointing device of claim 1, wherein the illuminating source is a light-emitting diode (LED) .

6. The pointing device of claim 5, wherein the diode emits white light.

7. The pointing device of claim 1, wherein the sensor means is a CMOS sensor.

8. The pointing device of claim 1, wherein the processor is implemented by a Digital Signal Processor (DSP) .

9. The pointing device of claim 1, further comprising a connection means for transferring data from the pointing device to another device.

10. The pointing ■ device of claim 9, wherein the connection means comprises a wireless connection.

11. A system for determining coarse absolute location information of a pointing device in addition to its relative displacement, comprising: - a surface divided into a plurality of non-overlapping fields, wherein each field is associated with a unique color information, and - a pointing device capable of being moved over the surface and comprising an illuminating source for illuminating a portion of the surface, said portion corresponding to the actual location of said device over said surface; a sensor means for sensing a reflected light from said illuminated portion and designed to deliver different sensed signals in response to each of the unique pieces of color information; and a processor associated with a memory storing a comparison table between each of said unique pieces of color information and the fields associated with said unique pieces of color information, and using said sensed signal to identify the associated field ^• on the basis of the comparison table and to deliver thereby a coarse location information.

12. The system of claim 11, wherein the color information comprises the color of the respective field. .

13. The system of claim 11, wherein the color information comprises a pattern made up of at least two distinct colors applied in the respective field.

14. The system of claim 12, wherein the surface is a side of a sheet of paper with the fields applied thereon in conformity with the color information.

15. The system of claim 13, wherein the surface is a side of a sheet of paper with the fields applied thereon in conformity with the color information.

16. A meth^'od for determining coarse absolute location information of a pointing device in addition to its relative displacement on a surface, the method comprising: placing the pointing device on said surface divided into a plurality of non-overlapping fields, wherein said fields are uniquely associated with color information, and wherein the pointing device comprises an illuminating source, a sensor means and a processor associated with a memory storing digitally said color information of all the fields; illuminating a portion of the surface by the illuminating source as the pointing device is moved over said surface; detecting reflected light from a spot of said illuminated portion by the sensor means, wherein the size of the spot is much smaller than the size of any of said fields, and generating a signal in response to the unique color information; transferring said signal to said processor; comparing said signal with the color information digitally stored; and determining the coarse absolute location of said pointing device on the basis of said comparison.

17. The method of claim 16, wherein the unique coloring of the fields is realized by coloring each field with a different color.

18. The method of claim 16, wherein the unique coloring of the fields is realized by coloring each field with a combination of at least two distinct colors, wherein at least one of said colors also differs from the colors used for coloring the remaining fields.

19. The method of claim 16, wherein white light is used for the illumination of said portion of the surface.

20. A mouse for determining coarse absolute location information in addition to a relative displacement thereof on a surface divided into a plurality of non-overlapping fields, the mouse comprising: a housing with a light-transmitting window formed in its underside facing to said surface; an illuminating source arranged within said housing for illuminating a portion of the surface through the window, said portion corresponding to the actual location of the mouse over said surface; a sensor means arranged within said housing in the immediate vicinity of said illuminating source for sensing a reflected light from said illuminated portion through the window and designed to deliver different sensed signals in response to each of a plurality of unique pieces of color information associated with said fields of said surface; and a processor connected with said sensor means and associated with a memory storing a comparison table between each of said unique pieces of color information and the field associated with said unique pieces of color information, and using said sensed signal to identify the associated field on the basis of the comparison table and to deliver thereby a coarse location information.

21. The mouse of claim 20, wherein the illuminating source is a light-emitting diode (LED) .

22. The mouse of claim 20, wherein the sensor means is a CMOS sensor.

23. The mouse of claim 20, further comprising a connection means for transferring data from the pointing device to another device.

24. The mouse of claim 23, wherein the connection means comprises a wireless connection.

25. A digital pen for determining coarse absolute location information in addition to a relative displacement thereof on a surface divided into a plurality of non- overlapping fields, said pen comprising: a tubular housing having a closed end and an open end; a tip forwardly protruding from the housing at the open end and contacting said surface; an illuminating source arranged within said housing in the open end thereof for illuminating a portion of the surface, said portion corresponding to the actual location of the pen on said surface; a sensor means arranged within said housing in the immediate vicinity of said illuminating source for sensing a reflected light from said illuminated portion and designed to deliver different sensed signals in response to each of a plurality of unique pieces of color information associated with said fields of said surface; and an electronics connected with said sensor means comprising a processor associated with a memory storing a comparison table between each of said unique pieces of color information and the field associated with said unique pieces of color information, and using said sensed signal to identify the associated field on the basis of the comparison table and to deliver thereby a coarse location information.

26. A digital pen of claim 25, further comprising an ink forming element for creating pen strokes when said tip is moved on said surface.

27. The digital pen of claim 26, wherein the illuminating source is a light-emitting diode (LED) .

28. The digital pen of claim 26, wherein the sensor means is a CMOS sensor.

29. The digital pen of claim 26, further comprising a ^' connection means for transferring data from the pointing device to another device.

30. The digital pen of claim 29, wherein the connection means comprises a wireless connection.